I came across a free tool that can help import free .stl files into Pattern Sculptor.

A potential customer is looking for a replica monado sword (Google it). I found several free .stl models online, but most of them resulted in an error when I tried to open them with Pattern Sculptor. One of the model creators mentioned this web site: https://netfabb.azurewebsites.net/. It's a Microsoft online tool, and you need a free Microsoft account to use it, but it worked for me. I was able to open a couple of models that previously resulted in an error after using this tool.